READ • REASON • RECORD
Measurement Lab
Build a measurement you can explain. Work through one module at a time.
Predict → try → explain
Will moving the object change its length? Will moving your eye change the apparent endpoints?
The object sits above the scale. Change viewing position to see geometric parallax; its true length stays fixed.
Read both ends
Scale resolution: 1 mm (0.1 cm). Use the endpoint difference, even when the object does not start at zero.
Accessible scale readings / 3D fallback
At perpendicular view: left 1.0 cm; right 6.4 cm. Side views change apparent alignment only.
Resolution, accuracy and precision
Resolution is the smallest displayed increment; precision is repeatability; accuracy is closeness to an accepted reference. Repeating a biased measurement does not correct it. Vernier calipers and micrometers are planned for a later phase.
Predict → try → explain
Which volume method suits a regular block, a sinking stone and a sponge? Predict whether an attached air bubble makes the calculated density too high or too low.
Read the bottom of the concave meniscus at eye level. The stone is nonporous and sinks. Water level rises by the immersed volume when fully submerged; the rock shape is illustrative.
Accessible scale reading / 3D fallback
35 cm³ at the bottom of the meniscus.Displacement method
Convert and report
Keep guard digits during calculations. Report a sensible final precision based on the measurements; exact conversion factors do not limit significant figures.
Spot the problem
Predict → try → explain
How will increasing length affect period? Why might timing ten complete oscillations be more reliable than timing one?
Same bob; small-angle model, g = 9.81 m/s². Length is pivot to bob centre. The centre line marks a reference position: count returns in the same direction, starting at zero.
Start motion explicitly, including with reduced-motion settings. Pause is always available. Small-angle period is approximately independent of amplitude here; this does not hold for every angle.
Time complete oscillations
- Use at least five lengths. Keep the bob and release angle unchanged.
- Start at a centre crossing. Count zero, then returns in the same direction.
- Time ten oscillations three times at each length. Preserve unexpected readings and repeat.
Manual stopwatch uses elapsed real time and your start/stop reactions; it does not automatically stop at 10 cycles. Displaying hundredths does not imply 0.01 s accuracy.
Separate ideal-model timing
Timing uncertainty: one versus ten
At this length, using ideal durations for comparison: one oscillation → 14.1%; ten → 1.4%. Fractional uncertainty = timing uncertainty ÷ total measured time. The same total reaction uncertainty is assumed, not measured.
Start and stop delays can cancel or introduce bias. More repeats do not guarantee every new mean is closer to the true value.
Investigation table
0/5 distinct lengths have three readings. Raw times are retained; derived values use unrounded means. Additional sets at the same length are kept as explicit repeats.
| L / m | 10 cycles: t₁ / s | t₂ / s | t₃ / s | Mean / s | T / s | T² / s² | Origin |
|---|
Source practice values are periods from the notes, converted to ten-cycle times. They are not your manual trials and are not three repeated measurements.